In the face of access demand of future composite combined services, the passive optical network technology becomes a predominant technology for developing Fiber To The Home (FTTx) due to its natural advantages of high bandwidth and full service access capacity. Wherein, a PON system needs to provide electric interfaces such as E1/T1, even SDH/SONET optical interfaces to develop relative services, in order to meet the demands from business customers on Time division Multiplex (TDM) services (such as an E1/T1 private line), particularly, when it needs to join with a traditional Synchronous Digital Hierarchy (SDH)/Synchronous Optical Network (SONET) based is multi-service transmission platform network.
Generally, a PON system employs Circuit Emulation Service over Packet (CESoP) to provide access of TDM services. In addition to high-level service quality requirements of TDM services, such as low delay and no error code, nondestructive protection for services is also an important requirement. The above CESoP includes E1/T1, SDH/SONET optical interfaces, and etc. At present, a common method of realizing TDM service protection in a PON system is that the protection for CESoP service flows is realized through an existing PON physic port, or realized through port mirroring by utilizing the exchange function of internal layer 2 (L2). However, protection switching time cannot be guaranteed within 50 ms, TDM channel-level protection cannot be realized, and the practicality is poor, due to the existing of the problems, such as, an Optical Network Unit (ONU) may become online again and MAC address learning are involved.